The postdoctoral research training program in Endocrinology and Diabetes at the Massachusetts General Hospital provides intensive research experience in basic or clinical investigation, complemented by a didactic component appropriate to the training goals. The trainees are primarily M.D.'s and M.D./Ph.D.'s who desire a career in investigative endocrinology and academic medicine, as well as Ph.D.'s who want further research training. The trainees are selected from a large applicant pool on the basis of prior academic and/or research achievement, and evidence of strong commitment to a career in biomedical investigation. The Program director (J. Avruch) is a senior academician and endocrine investigator who governs in conjunction with a committee of experienced endocrine scientists (Habener, Kronenberg, Crowley, Neer, Freeman, Grinspoon and Klibanski). The faculty consists of 49 active, well-funded scientists, whose interests range broadly across the subdisciplines of endocrinology, and from clinical, bedside investigation to molecular mechanisms. The trainees are supervised closely by a primary faculty mentor, and interact extensively with junior faculty, who often serve as secondary mentors. An extensive program of didactic sessions complements the research activity. The training period is 2-3 years but may include several years additional experience at junior faculty status, so as to permit consolidation of skills and maximal competitiveness for independent support. The productivity of past trainees during training has been very high overall, as judged by the number and quality of trainee publications. The majority of program graduates remain in academia and a substantial number are in the biotechnology/pharmaceutical industry. Among those in academia, about one fifth of graduates since 1999 have an RO-1 and about two fifths have achieved transitional independent support, a usual precursor to RO-1 support. The facilities at the MGH are extensive, including an Institutional Clinical Research Support Program and over 50,000 square feet of modern laboratories dedicated to endocrine training faculty. This training grant is the central stabilizing financial element in this program, and is especially critical in enabling M.D. trainees to achieve careers in biomedical investigation.